Pine gum distillation



J1me 1952 L. A. GOLDBLATT mm. 2,593,684

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INVENTORS L. A .GOLDBLATT N .C MQGONNELL H- B.SUMMERS JR.

BY 1.11m...

ATTORNEY Patented June 3, 19.52

PINE GUM DISTILLATION Leo A. Goldblatt, New Orleans, La.,.and Nealy C.McConnell, Olustee, and Hugh .3. Summers, J r., Lake City, Fla.,.assignors to the United States of America as represented by theSecretary of Agriculture Application May 11, 1950, Serial .No. 161,442

(Granted under the act of March 3, .1883, as amended April 30, 1928;3'70 0. G. 757) 4 Claims.

This inventionrelate's'to the distillation of pine gum, and moreparticularly to the production of gum spirits of turpentine havingimproved quality. It'has among its objects a purification-treatment ofthe vapor stream exiting from either batch or continuous steam stills toproduce a turpentine of improved color and exceedingly low acidity.

When pine gum is distilled in conventional equipment used in theindustry the turpentine obtained (gum spirits of turpentine) containsacidic impurities. The acids present are of two types, water-solubleacids, which are chiefly acetic and formic acids, and water-insolubleacids, which are chiefly resin acids of the formula CzoHzoOz. Thisacidity is one of the principal causes of turpentine deterioration anddiscoloration when placed in metal containers.

The amount of acid present in the turpentine varies considerablydepending chiefly upon the care taken during distillation of the pinegum. Nevertheless, even when the greatest care is taken the turpentinewill typically have an acid number of about 0.5 or greater with presentmethods. The acidity of certain samples of commercial gum turpentine hasbeen found to exceed the acid number of 3.1. Typical acid numbers ofturpentine obtained with the best commercial practice available prior toour invention are about 0.6 to 0.7, of which the water-soluble acidnumber is usually about 0.1 and the water-insoluble acid number is about0.5 to 0.6.

The acid concentration in the turpentine is not constant during thedistillation of a batch of pine gum, and increases markedly as thedistillation progresses. The turpentine obtained at or near thebeginning of the distillation is relatively low in acidity. Employingthe best previously known methods the initial acid number may beas lowas 0.1, whereas the last portion of turpentine obtained has an acidnumber reaching as high as 5.0 or even more. In a typical case in whichspecial care was taken and all previously known precautions employed toreduce the acidity, it was found that the turpentine obtained at theturning out point (i. e., when the ratio of turpentine to water in thedistillate was less than 1 to 10) had an acid number of 4.5.

The presence of appreciable acid in the turpentine is inherentlyundesirable for most of the purposes for which turpentine is used. Theacid attacks metal containers customarily used for storing and shipping,thus causing high corrosion losses, and moreover results in theintroduction of impurities in the turpentine. The acidity itself as wellas the introduced impurities affects unfavorably the value of turpentinefor solvent, paint, medicinal, and other purposes.

The water-insoluble acidity i believed to be due to the presence ofsmall amounts of resin acids in the turpentine, carried over unavoidablyin the vapor stream entering the condenser. In order to reduce theamount of entrained resin acids or rosin in thevapor stream exiting fromthe stills, it is customary to use centrifugal separators. These devicesare effective to remove quantities of rosin carried in the stream as aspray, but as previously mentioned, the best turpentine obtainable withthese or other similar devices possesses an acid number of from 0.6 to1.0 or greater. These devicesremove little or none of the volatilewater-soluble acids from the vapor stream, yet it is well recognizedthat they are incapable of reducing the water-insoluble acid numberbelow 0.5 or 0.6 in the final batch or in product processes.

According to our invention we have discovered that the acidity ofturpentine can be reduced to the order of 0.1 by employing a sectionpacked with glass fibers in the vapor line of the still. Such a sectionhas a peculiar effect upon the turpentine recovered in the condenser. Itacts as a scrubber, yet its total effect is greater than this. Forexample, the Water-soluble acidity as well as the water-insolubleacidity is markedly decreased. This fact is particularly surprisingsince the water-soluble acids, chiefly acetic acid, and to a lesserextent formic acid, have a lower boiling point than does turpentineitself. One would naturally expect that our packed section would not.afiect the quantity of water-soluble acids present in the turpentine.We have discovered. however, that our section is capable of decreasingthe water-soluble acids by 50 percent or even more.

In following our process we may employ a turpentine-sti-ll of any of theusual steam distillation types, either batch or continuous, andoperating at atmospheric pressure or at pressures above and belowatmospheric. conditions of distillation rates and temperatures, amountsof open steam, and the usual methods of charging and feeding the gum.

Our packed section is preferably placed in the vapor line of the stillat a point near the outlet of the distillation chamber or still. Thesize of the packed section varies with the size and capacity of thestill; its specific dimensions depend chiefly on the vapor throughput.In general, the cross-sectional area, measured perpendicular to We mayemploy the usual' the direction of vapor flow, is preferably such that hthe vapor velocity should be less than 5 feet/second thus, to promotecontact with the glass packing. The depth of the packed section shouldbe adequate to remove substantially all entrained material, for we havefound that when this result is accomplished, the atmnding desirableeffects of the packing on the vapor stream are also accomplished. Itmust be kept in mind that our packed section functions not merely as ascrubber since its effect upon the vapor stream is more than merelymechanical removal of spray or other non-vaporous material.

In operation, the vapor passing through the packed section is relievedof spray particles and other non-vaporous material. In addition, a verysmall amount of condensate usually occurs as a result of thermal lossesto the atmosphere at the extreme outside portion of the section. Thiscondensate will then drain back into the still, but the amount is verysmall and does not affect the successful operation of the distillation.

The temperature maintained within the section may vary within widelimits. For practical purposes no additional temperature control isnecessary further than the maintenance of temperature inherentlyresulting from the heated vapor stream passing through it. Thetemperature is always below the normal boiling point of the rosin, andas a practical upper limit we mention 350 F. Moreover, the temperatureis maintained above the normal melting point of rosin and, with theexception of the extreme outer portions previously mentioned where someinsignifiicant condensation may occur, the temperature is maintained sothat the turpentine and water in admixture are in the vapor phase.

Particular advantages characterizing the present invention are aturpentine of vastly improved quality. Furthermore, the packed sectionmay be employed without special attention over long periods of time. Inaddition, our packed section eliminates special devices such ascentrifugal separators designed to operate with particles in the vaporstream.

The apparatus employed in carrying out our invention is described by theaccompanying drawing.

Referring to the figure, I refers to a conventional pine gum stillcontaining steam heating coils and provided with an inlet forintroducing steam or water. The packed section is illustrated by 2. Itcontains glass wool or fibers loosely packed and held in place byretainer members 3 and 4, which may be screens or perforated plates.Vapors exiting from the still passes through the packed section intocondenser 5 of conventional design. The vapors are condensed by theaction of cooling water flowing through the condenser. The turpentine iscollected at 6 where the turpentine and condensed steam separate intotwo immiscible layers. An opening I is provided to permit washing theglass packing with steam, turpentine, or any suitable solvent forremoval of entrained materials.

The following specific examples illustrate the invention:

Example 1.-A packed section containing 55 pounds of Fiberglas insulatingwool Type TW-F, packed to a height of 3 feet in a tube measuring 22inches outside diameter was inserted in the vapor line of a smallcommercial still. A charge of 2500 pounds of pine gum was distilled overa period of 50 minutes. The turpentine was found to have a total acidnumber of 0.09, of which the water-soluble acids contributed 0.02 andthe water-insoluble acids 0.07.

The same weight charge of pine gum from the same source was distilled inthe same still at the same rate, but without the use of the packedsection. The acid number of the turpentine from a number ofdistillations varied from 0.6 to 0.75. The water-soluble acid number ofthe turpentine averaged about 0.06.

Example 2.-A packed section such as illustrated in the accompanyingdrawing was installed in a commercial still. This section measured 3feet in diameter and 4 feet in height. It was packed with 1'79 pounds ofFiberglas insulating wool, Type TW-F. The turpentine obtained from thestill under normal batch operation had an acid number of only 0.09, ofwhich the water-soluble acidity was 0.01 to 0.02, the remaining beingwater-insoluble acidity. These values are typical and are representativeof a large number of distillations carried out on this particular still.

In contrast to the above results, this same still before installation ofour packed section produced turpentine consistently possessing an acidnumber of 0.75, of which the water-soluble acidity was 0.05 and thewater-insoluble acidity was 0.70. Before installation of our packedsection this still was provided with a centrifugal separator in thevapor line.

The invention herein described may be manufactured and used by or forthe Government of the United States of America for governmental purposesthroughout the world, without the payment to us of any royalty thereon.

Having thus described our invention we claim:

1. The method of distilling pine gum comprising vaporizing theturpentine in the pine gum by 'means of heat and steam thereby producinga stream comprising turpentine and water vapors, passing this vaporstream through a zone packed with glass fibers, condensing the vaporstream, and recovering turpentine from the condensate.

2. In the process of steam distilling pine gum in which a condensatecomprising water and turpine is obtained and a residue comprising rosinis obtained, the steps which comprise passing the vapor stream exitingfrom the still and comprising water and turpentine vapors through a zonepacked with glass fibers suflicient to remove substantially allnon-vaporous particles from said stream thereby purifying the turpentineby reducing its water-insoluble and Water-soluble acidity.

3. The method comprising vaporizing the turpentine in pine gum by maensof heat and steam, passing the stream comprising turpentine vapor, watervapor and rosin particles through a zone presenting multiple passagesand scrubbing surfaces of glass fibers, the depth of the zone being atleast sufficient to remove substantially all entrained material, thetemperature in the zone being below the normal boiling point of therosin and above the melting point of the rosin, the turpentine and waterin said zone being in the vapor phase, condensing the vapor stream, andseparating turpentine from the water condensate.

4. The method of distilling pine gum comprising vaporizing theturpentine in the pine gum by means of heat and steam, thereby producinga stream comprising turpentine and water vapors, passing this vaporstream through a zone presenting multiple passages and scrubbingsurfaces of glass, fibers, the vapor velocitybeing leess than five feetper second therein, to promote extended contact with the glass surfaces,the temperature Within the glass packed zone being below 350 UNITEDSTATES PATENTS F. and above the normal melting point of rosin, NumberName Date the water and turpentine being in vapor phase in 235 521 Fox14, 1880 said zone, and thereafter condensing the water 1,1111%; CastonaSept-'22, 1914 vapor and recovering turpentine, whereby the 5 1,258,562Harris Man 5, 1913 turpentine is purified by reducing its water-in-2,272,503 Bays Feb 10,1942 soluble and water-soluble acidity. 2,308,715Reed Jam 19 1943 HUGH B. SUMMERS, JR. 10 Industrial and EngineeringChemistry, Analytical edition, vol. II. No. 5, May 1939, pages 289-REFERENCES CITED 290. The following references are of record in theChemical and Metallurgical E e r Febfile of this patent: y pages144-146.

